Retrograde (music)
（重定向自Cancrizans）
A musical line which is the reverse of a previously or simultaneously stated line is said to be its retrograde or cancrizans ("walking backward", medieval Latin, from cancer, crab). An exact retrograde includes both the pitches and rhythms in reverse. An even more exact retrograde reverses the physical contour of the notes themselves, though this is possible only in electronic music. Some composers choose to subject just the pitches of a musical line to retrograde, or just the rhythms. In twelve-tone music, reversal of the pitch classes alone—regardless of the melodic contour created by their registral placement—is regarded as a retrograde.